More than half the world's freshwater reservoirs are projected to become functionally dead by 2060 due to sediment accumulation. The finding comes from an analysis of over 550,000 reservoirs using satellite imagery and machine learning.
Researchers led by Kai Liu at the Chinese Academy of Sciences determined that reservoirs lose more than 36 cubic kilometres of capacity each year. This volume matches the size of China's Three Gorges Reservoir. A reservoir is considered functionally dead once sediment fills over half its volume. Australia and Spain face the highest risks. Nearly 85 per cent of Australian reservoirs and three-quarters of Spanish ones are expected to reach this threshold by 2060. In arid regions overall, nearly three-quarters of reservoirs may become non-functional. The study estimates the world loses over 7 per cent of its freshwater storage capacity each decade. This threatens water supplies for more than 2 billion people and over a quarter of global irrigated land. Solutions proposed include upstream reforestation and dredging, with costs potentially reaching $100 billion.